Laid-Open Japanese Patent Application Publication No. 2010-101990 discloses a tandem type color printer. The color printer has a main casing, and, within the main casing, four photosensitive drums for colors of yellow, magenta, cyan, and black are arranged parallel to each other. Four developing cartridges are provided in the color printer so as to have a one-on-one correspondence to the four photosensitive drums. Each developing cartridge has a developing roller for supplying toner to the corresponding photosensitive drum.
Such a tandem type color printer includes a retaining member provided in the main casing for collectively retaining the four developing cartridges. The retaining member is configured to be movable in a horizontal direction between the inside and the outside of the main casing. When any of the developing cartridges has run out of toner, the retaining member is pulled outward from the main casing, and the developing cartridge is removed from the retaining member, and a new developing cartridge is mounted in the retaining member.
Printer manufactures are recently urged to meet demand for cost reductions and environmental concerns. In terms of cost reductions and environmental concerns, it is desirable to employ a toner cartridge replacing system, in which only a toner cartridge for accommodating toner is replaced without replacing the developing roller, rather than to replace the developing cartridge with a new one, when toner has run out.
The toner cartridge is formed with an opening for discharging toner therefrom. Further, the toner cartridge is provided with a shutter for opening and closing the opening. When the toner cartridge has been removed from the retaining member, the shutter is moved to a closed position in confrontation with the opening, thereby closing the opening. This configuration prevents toner accommodated in the toner cartridge from leaking out through the opening. When the toner cartridge has been mounted in the retaining member, in order to supply toner accommodated in the toner cartridge to the developing roller, the shutter is moved to an open position not in confrontation with the opening, thereby opening the opening.
Hence, in the toner cartridge replacing system, the shutter is required to be closed when the toner cartridge is removed from the retaining member and to be open when the toner cartridge is mounted in the retaining member. Accordingly, an operation unit is required to operate the shutter to move between the open position and the closed position.